The present invention is related to a method of loading a material into a bibulous reservoir useful for drug delivery and more particularly into a method for loading a medicament into an iontophoretic reservoir-electrode and a iontophoretic reservoir-electrode formed by the method.
Iontophoretic delivery of a medicament is accomplished by application of a voltage to a medicament loaded reservoir-electrode, sufficient to maintain a current between the medicament loaded reservoir-electrode and a return electrode (another electrode) applied to a patient""s skin so that an ionic form of the desired medicament is delivered to the patient.
Shelf storage stability problems for many of the iontophoresis devices reported in the literature require that the medicament be stored separately from the reservoir-electrode until immediately prior to use. lontophoretic delivery of medicaments is recognized as desirable for many medicaments, but it is not widely used because no devices are commercially available that meet all of the needs of the potential user population. An important requirement for a product to enjoy widespread usage is shelf storage stability. If a drug product is not stable under normal shelf storage conditions, it is unlikely to be a successfully commercialized product because the short shelf life limits the product""s utility to most potential users as most of the product""s useful life is exhausted during the time required for manufacturing and the distribution process. Thus, determination of shelf storage stability is an important part of a drug product""s regulatory approval process. If there are difficulties with storage stability, regulatory approval may be withheld. Often, the reservoir-electrode also is maintained in a dry (unhydrated) condition prior to use also because of the tendency of the active electrode material to undergo physical and chemical changes during shelf storage. The need to store the several components separately has limited the use of iontophoretic devices, since in order to use the device, the reservoir-electrode needs to be charged with the medicament and hydrated either by a practitioner or user immediately prior to use. There are regulatory requirements related to the accuracy and precision of content of a particular drug in an individual dosage form. When a drug dosage form is a tablet, there are specific requirements related to weight variation, dissolution, content and stability. Parenteral dosage forms require concentration assay and stability. Other more complex dosage forms such as transdermal or iontophoretic delivery devices are developing similar standards, but the problems related to loading the devices and the stability of the charged devices are continuing problems.
Several United States Patents disclose devices that attempt to overcome the problem of shelf storage stability and facilitate the preparation of the device for use. U.S. Pat. No. 5,320,598 discloses a dry-state iontophoretic drug delivery device that has drug and electrolyte reservoirs that are initially in a non-hydrated condition. The device has a liquid containing pouch or breakable capsules that contain water or other liquid, the liquid being releasable by disrupting the liquid containers prior to use. Commercial manufacture of a device utilizing this disclosure would be complex.
U.S. Pat. No. 5,385,543 also discloses a dry-state iontophoretic drug delivery device that has drug and electrolyte reservoirs. The disclosed device includes a backing layer with at least one passageway therethrough that allows the introduction of water or other liquids into the drug and electrolyte reservoirs prior to use followed by joining the reservoirs to the electrodes. The patent teaches that by joining the reservoirs to the electrodes after hydration, delamination problems are reduced.
No commercial products utilizing the technology disclosed either in the ""598 or the ""543 patents have been produced.
A different approach to the shelf storage stability problem is disclosed in U.S. Pat. No. 5,817,044. In this disclosure, the device is divided or otherwise separated into at least two portions, with one portion containing the electrode reservoir and the other containing the drug reservoir, which may include a medication in a dry form. In this disclosure, the user causes the two portions to come into electrical conducting contact with one another to at least partially hydrate one of the reservoirs, by either folding the device to bring the two portions into contact with one another or by removing a barrier dividing the two portions. While this device is somewhat seems to be somewhat easier to use than the devices disclosed in the above patents, there currently is no commercial device that utilizes this disclosure.
International Application WO 98/208869 discloses an iontophoretic device for delivery of epinephrine and lidocaine HCl. The disclosed device includes materials that deter microbial growth and anti-oxidants to enhance the stability of epinephrine. While this disclosure recognizes the need for shelf storage stability and addresses the problem of epinephrine stability by including anti-oxidants, there is no teaching of the need or ability to uniformly load the reservoir-electrode. Again, there is no commercial product based on the information in this disclosure.
A further problem related to production of a successful commercial pharmaceutical product is related to the requirements for accuracy and precision of dosage. In some of the iontophretic drug delivery devices described above, the user or the practitioner is required to perform some action to hydrate the reservoir-electrode and introduce the medicament introduce the medicament to be delivered into the delivery device prior to use. Such operations that depend upon the practitioner or user to charge the medicament into the device under relatively uncontrolled conditions may result in improper dosing. Regulatory requirements for pharmaceutical products generally specify that not only medicaments contain between ninety and one hundred-ten percent of the label claim, but also that the delivery be uniform from sample to sample.
It is well recognized that many medicaments are not stable to conditions necessary for assembly and storage of iontophoretic reservoir-electrodes. A method of accurately and repeatedly loading the medicament and any required stability enhancing excipients during the assembly process of reservoirs useful for passive transdermal drug delivery and reservoir-electrodes for iontophoretic drug delivery devices that was compatible with a mechanized assembly process and also provided a charged reservoir-electrode with satisfactory stability properties would represent an advance to the art of delivery of medicaments. By providing a stable ready-to-use device as disclosed below, the method of the invention substantially eliminates used induced variability due to loading. Summary A method of the present invention for loading a material into a hydrophilic transdermal medicament delivery reservoir includes providing a transdermal delivery device including a backing with an interior surface that has a bibulous reservoir having a patient contact surface disposed on the inside surface. The method of the invention further includes placing a section of an absorbent material on the patient contact surface of the bibulous reservoir, applying a preselected aliquot of a material to be charged into said bibulous reservoir onto the absorbent material and allowing the absorbent reservoir having the absorbent material with the aliquot of the material applied thereto to stand for a sufficient time for the material to be absorbed into the bibulous material, thereby loading the material into the reservoir.
A method of the present invention for loading a material into an iontophoresis reservoir-electrode includes providing an iontophoresis reservoir-electrode including a backing with an interior surface having an electrode thereon and a bibulous reservoir having a patient contact surface with a shape disposed on the interior surface of the backing in electrical contact with the electrode. The method also includes providing a closure sized and shaped to engage the backing for forming a releasable seal to isolate the bibulous reservoir from the ambient environment, the closure is removable from the housing to expose the patient contact surface for use. The provided closure has an inside surface with a section of an absorbent material disposed thereon. The provided section has a first surface with a similar shape to the contact surface of the bibulous reservoir so that when the closure is disposed on the backing, the absorbent material first surface is positioned in intimate physical contact with the contact surface of the reservoir. The method further includes applying a preselected aliquot of a material to the absorbent material on the inside surface of the closure and placing the absorbent material on the patient contact surface of the reservoir. The method also includes allowing the reservoir-electrode with the closure applied thereto to stand for a sufficient time to allow the aliquot of the material to be absorbed into the bibulous reservoir thereby loading the reservoir-electrode.
An iontophoresis reservoir-electrode of the invention includes a backing with an interior surface including an electrode, a bibulous reservoir that has a patient contact surface with a shape disposed on and in electrical contact with the electrode. The reservoir-electrode is charged with a preselected aliquot of a material and has a closure that is sized and shaped to isolate the bibulous reservoir from ambient environment. The closure is removable from the backing to expose the patient contact surface for use. The closure has an inside surface with a section of an absorbent material disposed thereon. The section has a first surface with a similar shape to the contact surface of the bibulous reservoir and with the closure disposed on the backing, the absorbent material first surface is positioned in intimate physical contact with the contact surface of the bibulous reservoir and removed from the patient contact surface of the bibulous material when the closure is removed from the backing.
The device formed by the method of the invention overcomes the problem of reliably applying the correct amount of the desired materials to passive transdermal reservoirs and for iontophoretic devices. Both the medicament and excipients for the active reservoir-electrode or the materials necessary for the return reservoir-electrode are accurately and precisely loaded into the reservoir. Many materials that are suitable for forming the reservoir are cross-inked by the application of ionizing radiation or require application of thermal energy in forming. If the medicaments are mixed with the material before forming or cross-linking, the medicament is exposed to the forming conditions, i.e., ionizing radiation, thermal energy, chemically reactive cross-linking agents and the like, that may adversely effect the medicament. Thus there is a need for a method of loading the transdermal reservoir or the iontophoretic reservoir-electrode after the reservoir is formed. The method of the invention uniformly loads the reservoir-electrode of the invention during the assembly process, improves the efficiency of assembly of both passive transdermal reservoirs and iontophoresis reservoir-electrodes and is compatible with the high-speed assembly line manufacture necessary for a successful commercial product. The method and the device of the invention greatly improve the efficiency of assembly of complete medicament loaded reservoir-electrodes and thus advances the art of iontophoretic drug delivery by making a prefilled ready-to-use device available that fulfills the regulatory requirements of accuracy and precision.